Why can't I get a clean result from cycles?
Either crank up your samples or try denoising with AI or Photoshop / AfterEffects.
The former takes a little longer to render, the latter produces artifacts at times.

I am not too sure about the current implementation of denoising into cycles, but there is an addon called dnoise you could try out. Otherwise go into the "Properties" Editor, into the "Render" Context and and put a higher value into the "Render" textfield under "Sampling".

The thing is, that Cycles does a lot more realistic calculations than BlenderRenderer ever did, so it takes longer to produce a clean result...